January 18, 2012

Scientists Get Ready To Image A Black Hole

by editor

Astronomers are building a virtual telescope as big as our planet that will capture the first ever picture outlining an enormous black hole within our galaxy.

The Event Horizon Telescope will be powerful enough to see all the way to the center of the Milky Way, where the super massive black hole lives. Researchers believe by capturing an image of the black hole, it will allow astrophysicists to put Einstein´s General Theory of Relativity to the test.

Scientists from related fields around the world are gathering in Tucson, Arizona Jan. 18-20 to discuss the possibility, which would have been considered an outrageous concept as early as a few years ago. Dimitrios Psaltis, an associate professor of astrophysics at the University of Arizona´s Steward Observatory, and Dan Marrone, an assistant professor of astronomy at Steward Observatory, are organizing the conference.

“Everybody's super-excited,” said Psaltis. “A couple of years ago, this was science fiction. Now it's becoming a reality.”

“Even five years ago, such a proposal would not have seemed credible,” added Sheperd Doeleman in a press release on the University of Arizona's website. Doeleman is an assistant director of the Haystack Observatory at Massachusetts Institute of Technology (MIT), who is the principal investigator of the Event Horizon Telescope. “Now we have the technological means to take a stab at it.”

Observations of the black hole have to be done using radio telescopes sensitive to millimeter-scale wavelengths, because that is the ideal range for seeing through the dust and natural debris littering the center of the Milky Way, added Psaltis.

By combining the millimeter wavelengths from widely separated antennas, astronomers will be able to produce a picture of the Milky Way region unlike anything ever seen before. “We expect to see the swirling of matter going into the black hole in real time,” Psaltis told MSNBC's Alan Boyle. “What we're really hoping to see is how the black hole is fed.”

Black holes, objects that are so massive that nothing, not even light, can escape their gravitational pull, are created by enormous stars that collapse catastrophically, and possibly even take form when a galaxy forms. The black hole at the center of the Milky Way is thought to have a mass of 4 million suns, and even though humans have never seen it, scientists have been able to determine its location based on gravitational effects.

The black hole itself would appear as a black spot surrounding by a blazing swirl of inward-spiraling matter. Scientists say the Milky Way´s black hole is tame in astronomical standards, and that is a good thing for us. The violent galactic environment associated with more ferocious super-massive black holes wouldn´t be conductive to life as we know it.

The extent of the black hole in our galaxy is thought to be no more than the width of Mercury´s orbit around the sun, but by viewing the black hole from a distance more than 26,000 light years away, it would actually be like looking at a grapefruit on the moon, according to a news release from the University of Arizona.

“To see something that small and that far away, you need a very big telescope, and the biggest telescope you can make on Earth is to turn the whole planet into a telescope,” Marrone said.

Despite the enormous challenges facing scientists, they do believe the Event Horizon Telescope will prove promising, based on a pilot study conducted using the Steward Observatory´s Sub-millimeter Telescope in Arizona, the James Clerk Maxwell Telescope on Mauna Kea in Hawaii and the Combined Array for Research in Millimeter-wave Astronomy in California.

“Those three telescopes told us that we can actually observe all the way to the black hole,” Psaltis told me.

“In essence, we are making a virtual telescope with a mirror that is as big as the Earth,” Doeleman said. “Each radio telescope we use can be thought of as a small silvered portion of a large mirror. With enough such silvered spots, one can start to make an image.”

Astronomers now plan to bring in more telescopes to work on the project, including the 50-antenna Atacama Large Millimeter Array (ALMA) in Chile. Doeleman said ALMA´s participation will be a “real game-changer.”

“We will be able to actually see what happens very close to the horizon of a black hole, which is the strongest gravitational field you can find in the universe,” he told MSNBC. “No one has ever tested Einstein's general theory of relativity at such strong fields.”

Observing the bright outline that defines the black hole´s shadow could serve as an unprecedented test of general relativity, Psaltis said. “If we find the black hole´s shadow to be oblate instead of circular, it means Einstein´s General Theory of Relativity must be flawed.”

“But even if we find no deviation from general relativity, all these processes will help us understand the fundamental aspects of the theory much better,” Psaltis added.

Psaltis emphasized that they would not get a picture of the black hole all at once. Instead, data would emerge gradually as more and more readings are taken through the central data processing center at MIT´s Haystack Observatory. “In perhaps three years, we´ll be able to have the first complete picture of the black hole.”

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Image Caption: A computer simulation of superheated plasma swirling around the black hole at the center of our galaxy. (Image by Scott Noble/RIT)